iControl related to traffic flow and iRule applied

OK, so what is 'resource pool' please? Is it something monitored on the F5 itself?

In this case the Virtual server in scope has a pool with one member, the member is being monitored via TCP port 443 by F5.

OK, so, if the Pool Member (and thus the Pool as it's the only member) is down you want to terminate SSL and use your iRule (a redirect perhaps), if up, pass it through?

Would you be OK doing this with just an iRule? Shouldn't be too hard; check the Pool status on initial connection, if up, disable SSL and exit, if down, apply the logic in the rule you've already created. Sound good?

Are you suggesting something like this?

when CLIENT_ACCEPTED { if { [active_members ] =0 } { SSL::enable SSL::profile /Common/clientssl HTTP::enable } else { SSL::disable HTTP::disable } }

when HTTP_REQUEST { ... << display the maintenance page >> }

So, you need to use a standard Virtual Server with the required SSL profile and HTTP profile assigned and then yes, something very like what you've suggested;

when CLIENT_ACCEPTED { 

 If the Pool is up, pass it through and disable HTTP and SSL
 if { [active_members pool_name] > 0 } { 
  SSL::disable
  HTTP::disable
 } 

 If the Pool is down, do nothing and SSL will be terminated and the
 HTTP_REQUEST event will fire and display the maint. page
 else { 
  Do nothing
 }

}

when HTTP_REQUEST { ... << display the maintenance page >> }